Brake



June26,1945. Q QETZEL A 2,378,943`

I BRAKE Filed April '7,Y 1941 4 Sheets-Sheet lY C//n Geo/ye Oee 7 M, W,W7@

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A y .Potoniod .Inno 26,1945

John George Oetzel, Beloit, Wis., assignor to Warner Electric BrakeManufacturing Company, South Beloit', Ill., a corporation oi IllinoisApplication April 7, 1941, Scl-iai No. 387,1 87

30 Claims. (Cl. 188.-138) This invention relates generauy to frictionbrakes of the character commonly used 0n heavy duty automotive Vvehiclesand, in certain of its aspects, has more particular reference torbrakesof the type in which the primary actuating force isderived from themomentum of the part whose motion is to be controlled. The generalobject of the present invention is t to provide a brake of the abovegeneral character which may be constructed to produce a substan...

tially greater retarding eifect than prior brakes of similar character,in which the operating parts may be arranged'within the limited spaceavailable for brake equipment in modern vehicle wheels, which providesfor eilicient dissipation of irictional heat, which is self-adjustingthroughout the life of the friction linings, which lbecomesb applied ina minimum movement of the braked part following energization of theprimary momentum operator, and which is comparatively simple andinexpensive in construction and reliable in operation. In carrying outthis object, the invention contemplates the use of a torque amplifyingmechanism of novel character interposed between the controllablemomentum operator and the main brake and operable to amplify the derivedactuating force to the main brake with a mechanical advantage severaltimes as great as that obtainable with 4prior mechanisms, and thiswithout sacrifice in controllability of the brake.V

Another object is to provide a friction brake mechanism of theself-energizing type 'in which -the applied actuating force isYamplified to a substantially greater degree than in prior brakes withoutsacrificing controllability of the total retarding force.

A more detailed object is to providel an intermediate torque amplifyingmechanism' which detaken along the line ll-ll.

description taken in connection with the accompanying drawings, in whichFigure 1 is an axial sectional view of a brake embodying the novelfeaturesl of the present invention, the brake being shown disposedwithin a rotatable drum and the section being taken along the line I-iof Fig. 2. Figs. 2 and 3 are sections taken along the lines 2-2 and 3-30f Fig. 1.

Fig. 4 is a section taken along the line 4--I of- Fig. 2 with certain ofthe parts shown in section Fig. 5, is a fragmentary view similar toFissi showing the elements in actuated positions.

Figs. 6 and 7 arefragmentary perspective views of the main and auxiliaryfriction elements.

While the invention is susceptible of various modifications andalternative constructions, I

have shown in the drawings and will herein describe in detail apreferred embodiment. It is to be understood, however, that I.do notintend to limitthe invention by such disclosure but aim to cover allmodications and alternative constructions and uses falling withinth`spirit and scope of ,the invention as expressed in the appended claims.

The brake shown in the drawings as embodying the presentv invention isof the internal expanding type adapted to be use d with a'drum Il on thewheel 9 of a modern heavy dutyvehlcle. It comprises generally a mainfriction brake l0 adapted for gripping engagement with an internalsurface on the drum il, a momentum type friction operator 12,'preferably controlled electromagnetically, and a novel mechanism foraugi inenting many f old'the actuating force de rived by rivesasecondary actuating force from the mo- 'mentum of the part being brakedthrough the useoi -a'plurality or radially expen'sble and'circumierentlally spaced friction elementsindividually anchored andactuated.

, .Another object is to provide a brake in which the initial actuatingforcev is augmented in part by a self-energizing action and in Dart bydirect mechanical ampliiication whereby to preserve accuratecontrollability of the brake.

A The invention also resides in the novel arrangement oi.' the partsftoattain radial and axial compactnessand efficient heat dissipation.

Other objects and advantages of the invention will become apparent fromthe iollowingdetailed the operator and for utilizing the ampliiied forceto energize or expand the main brake I0. vAll of the movable parts aredisposed in a narrow radial space within the drum and :are arranged in anovel manner for eillcient dissipation of the Vheat generated when thebrake is applied.

'rho drumnas nn inturned aange n bolted to a vehicle wheel and near itsopen end provides f either exible or rigid; arranged in end-to-end aninternal Il adapted t0 be gripped by themen-rotatable friction elementof the main brake Il. Herein this element comprises two semi-circularshoes iiiFlgs. 1 and 2),

relation around the surface Il and' each ,compris- Inga curved band Ilhaving a segment." of friction material secured to its' outer surface. f

. The shoes are supported by an. anchor member in the form' of a castingIl fastened 4by bolts Il to a plate '2l which closes theopen end o! theparallel to the diameter 24.

.tractile springs 3D are stretched between lugs 3l is supported from the-the mediumof tangentially extending spring tact with the magnet Along adiameter-24 extending between theA pairs of adjacent shoe ends, theanchor member has two outwardly converging arms 25 each having a pair oispaced lugs 26 projecting laterally from its outer end. These -lugsprovide abutments 21 engageable with blocks 28 on brackets 29 weldedalong the inner surfaces of the shoe bands I6, the abutments Pairs ofcoiled consecured to the brackets 29 and urge the shoe ends to normalbrake-released position against the abutments 2i.

preferably extending .The operator l2 for'deriving the initial or priymary actuating force from the momentum of the moving vehicle comprisesdriving and driven friction rings 34 and 33 concentric with the drumaxis and adapted Afor axial gripping engagement, the degree of which maybe varied selectively to regulate the magnitude of the actuating forceand therefore the ultimate retarding effect. Preferably, the grippingengagement is produced -magnetically according to the degree ofenergizdisposed between the two' ation of a'winding 35 annular poles 36of the magnet ring. The pole faces 3l are flush with the surface offriction material 38 supported between thepoles. The magnet is mountedfor oscillation about the drum axis being in this instance carried by abushing 39 supported and backed by'a member 40.. For

l a purpose to appear later, this member is rotatably mounted on theexternal surface 4I of a cylindrical flange 42 integral with the anchorcasting I8. It be observed that the magnet is located near thev closedend of the drum and us axially spaced inwardly from the main brake Il).f

'I'he armature ring 34 is substantially dat and drum ange I3 througharms 43. These not only sustain the torque fric--l tionally applied tothe armature but continuously urge the latter intol light mechanicalconface.

The degree Vof gripping engagement between 'the rings 33 and 34 and,therefore, .the magnitude of the actuating force derived from themomentum of the vehicle is controlled by regulating the currentenergizing the magnet winding 35.` This may be accomplished by actuatinga control member such as a foot pedal 44 to adjust a rheostat 45 inthe'energizing circuit of the magnet which includes the vehicle battery45.-

In brakes of the mentation, the amplified force being then uti` vlizedto energize the main' brake I0. The operator 4 6 is a friction devicewhich operates with a self-energizing or wrapping action and, in thisinstance, is of `the'same general construction as with friction material48 and arranged end to' endv within the drum with their adjacent endsspaced apartrand disposed' on opposite sides of a diameter 5U which isat right angles to the diameter 24. To guide the shoes 48longitudinally, lugs 5I coact with yokes 52 secured to lugs 53projecting radially from the auxiliary anchor member 40 along thediameter 24. Arms 54 on this member project to points adjacent thedrumand each has integral therewith two laterally projecting spaced lugs54'. These provide oppositely facing abutments 55 engageable with plates56 on brackets 57 secured along the center line of the shoes 48.Contractile springs 58 normally maintain the shoes contracted. v

The primary actuating force derived by theV momentum operator I2 .may beapplied directly to energize the secondary operator 46. In thisinstance, however, the force is amplified by means of cranks 60 having ahub 6I pivoted on a pin 62 which is disposed between Vthe lugs 54'parallel to the drum axis and which is supported at one end by the arm54 and at the other end by a plate 63 connecting the lug ends. Inbrakereleased position, the cranks project inwardly along'the diameter50' and their free-ends are offset laterally so as tolie along the backof the magnet (Fig. 2). A` pin 64 rigid with the magl net projects intoan'elcngated slot 65 in the crank. Substantially in the plane of theshoes 48 and 4at points near the pivots 62, the cranks 60 carry pins 66which bear against the dat surfaces 61-of blocks B8 on the ends ofextensions 69 of the shoe brackets 51.' By virtue of these abovegeneralcharacter, the

prior practice has been to apply the primary ac- 'maintain the magnetconnections between the magnets and the shoeV ends, one -shoe 48 or theother is moved away from its anchor and the driven friction element ofthe secondary momentum actuator is expanded against the drum'as themagnet moves (see Fig. 5) in either direction aw y-from releasedposition. Contractile springs i the yokes 52 on the auxiliary anchormember 40 and elongated eyes 1I on the'magnettend to in the releasedposition shown in Fig. 4 and to return it to this position afterdeenergization.

. When-the shoes 48. are thus expanded into gripping engagement with thedrum, the surface '41 of the latter exerts a vfrictional force on theshoes tending to move the shoes and their supporting member 40 in thedirection of drum rotation. Such movement is permitted because of themounting of the auxiliary member 40 on the main anchor member I8 foroscillation about the axis. This frictional force is Vaugmented severaltimes by virtue of the self-energizing or wrapping action which buildsup progressively throughout the lengths of the relatively flexible shoes48. However, because the shoe surfaces do not exceed a semi-circle, thiswrapping action remains under control and the resultant force is alwaysproportional to the primary actuating 13 are pivoted lugs' 26 on the 'Instretched between ated and the shoes I5 expanded to energize the` mainbrake whenever the member 48 moves away from brake-released position.Contractile springs 8l stretched between lugsliiL on the floating anchormember 48 and stationary elongated eyes 82 welded at opposite ends tothe stationary anchor member I8 urge the member 40 toward brakereleasedposition while permitting freedom of' movement in either direction awayfrom ysuch position. 4

Assuming that the parts are in released positions (Figs. 1 to 4) thecomplete operation is as follows. When the magnet is energized, lthearmature 34 is attracted to the magnet with a force proportional to theenergizing current. As a result of such axial gripping, the drivingfrictional ring or armature 34 applies to the face of` known formulab=10-f1iiM where a is the angle,l of contact of the friction elementwith the drum-- The wrap factors are determined by the well surface andis thecoeiiicientof friction. In the brake shown, the factor (bi) forthe shoes 48 is approximately 2.68 while (ha) is about 2.04.

`Assuming, `for example, that C1 is 3.07, C: is

1.58, B/dm is 1.76, and da/dl is V1.13, the torque T.

the magnet 33 a friction force derivedfrom'the v momentum of therotating part .and directed circumferentially in the direction of drumrotation. The magnet ring moves actuating the cranks '60 and expandingthe shoes48 against the drum surface 41 as lshown in Fig. 5, after whichslippage occurs between the magnet and armature rings. y

Thus, the primary actuating force derived through the magnetic frictiondevice is not transmitted to themain shoes but instead is utilized toenergize the secondary momentumoperator Y 48 and` thereby cause -agreatly increased actuating force to be derived from the momentum of thevehicle by the self-energizing action which builds up in the shoes48while the latter lare, expanded. The frictional force thus applied tothe shoe surfaces by the drum causes the member 48 carrying the shoes toturn with the -drum and thus swing the cranks 13 to expand the main`shoes I5. When the latter become expanded fully (see Fig. 5), slippageoccurs between the shoes 48 and the drum surface 41, the augmentedactuating force continuing to be applied. Now.'

when'the magnet is deenergized, the parts areall returned to theirnormal positions by the springs 3D, 88,10 and BI. ,l j

The important partv which the intermediate momentum operator I6 plays inamplifying the torque (tm) derived frictionally by the momentum.operator I2 will be apparent from the following formulae: I

Y finis` thediameter of magnet betweenrcenters of on the auxiliary shoes48 would be 91.08-times the magnet torque and the torqueon the shoes I5would be 48.7 times this torque. Thus, for a magnet torque of 2085inch-pounds. the total torque A [tm(2085) -I-Ta(18,900) +T|u(101,500)

wcuid be 122,485 inch-pounds. It wmbe observar` that, in addition toconstituting the primary andil secondary actuating forces, the frictionforces.-

exerted on the driven elements of the momentum operators I2 and 46contribute to the total retarding force and that the secondary torque isa sub'- stantial proportion of the total. i

As a torque amplifier in the present environment, the intermediatemomentum operator 48 possesses numerous advantages over cams, levers,

or the like. In the first place, it is circular in form and its partsmove only circumferentially. Therefore, it may be arranged compactly inthe narrow radial space available within the wheel of a modernautomotive vehicle.

` shoes 48, the amplification is multiplied nine fold Secondly, itsmagnification of the torque is large due to the self-energizing actiondescribed above. With the half wrap friction elements or without anysacrifice in constancy of actionvor The brake above described may beconstructed controllability of the total braking effect.

Thirdly, it performs its function without necessitati'ng a correspondingmultiplication in the movement of the magnet and therefore of thevehicle in order to apply the brake.. Thus, when the friction surfacesof the brakev described above are new, the shoe clearances will be takenup and the brake applied by turning of theV wheel throughout fivedegrees following energization of the magnet. When the shoes are wornoif com'- pletely, about twenty-eight degrees is required.

This corresponds to about 9.2 inches of movement of the vehicle. Inother words, the torque applied by the main brake shoes I5 in retardingthe drum in the example given above is 48.7

times the primary actuating torque derived by the magnetic frictiondevice, whereas the movement of the magnet is only 5.6 times that of theactuated end of the main'brake shoes. Now, if the same amplificationy of`the magnet torque were produced by levers or other similar torquemultplying devices, a leverage ratio of 57.8 would be required and thevehicle movement required t0 set the brake' with the shoes worn outwould be about 35.5 inches. Such brakes.` would be unsuited for use inmodern traffic.` y

The friction type-of torque amplier isadjus'table automaticallyfor wearand does not require frequent servicing.- 'This is because wearing' offof the friction surfaces simply requires a further movementof the drumduring each brake appli- Y CatiQn."

in manyV capacities by tle use of many common parts. For example, toincrease its capacity, it

-is merely necessary to increase` the mechanical advantages -of thelever mechanisms .su .and 13.

'I'hisinvolves changes inl only a few of the parts. Also,the leverageratios may be distributed' inl 'any manner desired and the'frictionparts constructed for maximumeiliciency in dissipation equalized bymaking Istresses on the parts tage in spaced par and providing of thefriction heat created at the three dideren pairs of coactlng surfaces.

Y clings Il and 49 willy wear out approximately simultaneously and, atthe same time, the clearance between the shoes 48 and the drum, when theshoes` are worn, will be so small as not to require objectionably largemovement of the vehicle in setting the brake following energization ofthe magnet. For this purpose, the covering 49 is made relatively thin ascompared to the main shoe covering Il, approximately one-half thethickness of the latter or about one-fourth of an inch in the presentinstance. The total worn out clearance is thus limited and accordinglythe angular movement of the drum necessaryto set the brakes when thecovering 49 is exhausted. This reduction in thickness of the covering 49is compensated for and wearing out of the linings the coveringsufficiently wide to provide a substantially lower unit pres- -sure thanthat on the main shoes. Thus, with a magnet torque of 2085 inch-pounds,as in the example given above, and with the covering 49 I claim as myinvention: 1,.

` 1. A friction brake having. in combination, two l internal-cylindricalsurfaces axially spaced apart and rotatable about a common axis, twomain friction segments arranged yin end to end relation and expansibleinto gripping engagement with one o'f said surfaces, stationary stopsdisposed between said adjacent ends for anchoring one or the other end,cranks selectively engageable intermdiate their ends with Said segmentends and operable to expand said segments, a second pair of auxiliarysegments 'arrange/din end to end relation and expansible into grippingengagement with said otherrcylindrical surface, a member .mounted tooscillate about-said axis and conlnected to said cranks to actuate thelatter in.

the direction of rotation ofsaid surfaces. stops on said memberVselectively anchoring the ends of said auxiliary segments, cranksselectively engageable with the ends of said auxiliary segments andoperable to expand the latter, two friction elements adapted for axialgripping engagement, Y

one being rotatable with said cylindrical surfaces,

Vand means connecting the driven friction elecomposed of standardY brakelining 1.75 inches wide, it can be shown mathematically that the maximumpressure applied to the shoes 48 is' 105 pounds per square inch. If themain'shoe coverings Il are 4.5 inches wide, the unit pressure appliedthereto by the same magnet torque would be 265. Under these pressures,the covering 49 will wear down approximately one-half as fast as thecovering I'I ,and proximately the same length of service.

The arrangement of the parts as abovedescribed is advantageous from thestandpoint of radial and axial compactness, efficient heat dissipation,and ruggedness of construction. The magnetic momentum operator islocated within the two will giveapthe secondary or intermediate operatorwhich promotes axial compactness 'and minimizes the axial compactnessand ruggedness of mounting.

supporting the armature as member may be utilized to best advan Bydividing the friction element of the secondary momentum operator into aplurality of annularly individual anchors and actuators for these parts,the wrapping'action is kept within controllable As shown, the

veffective wrap angle of each part is greaterthan a right angle and lessthan 180 degrees so that the self-energizing action is an importantfactor in effecting torque amplication` and yet controllability of theVbrake is not sacrificed. .It will be observed that the. torqueamplification between the magnetic momentum operator andthe main brakeshoes is'effected in part by self-energizing action and part by directmechanical augmentation of a fixed ratio produced by the levers and 13.By such division, a high ampllcationfis obtained while insuring greatercontrollability than would be possible if the same amplication were'produced by self-energizatlon alone. Mounting on the magnet 33 on themovable anchor member 40 permits the bearing support 4| for this memberto be of maximum axiallength and therefore possess maximum risidlty.

ment to the cranks of said auxiliary segments.

2. A friction 'brake having, in combination, two internal cylindricalsurfaces rotatable about a common axis and disposed with their centerlines offset axially from each other, a main friction member expansibieinto gripping engagement with one of 'said surfaces, :stationaryanchoring means for said member, Vexpanding means for said member, apair of segments arranged in end to end relation and -expansible infogripping engagement with said other cylindrical surface, an said.axisand connected to said Aexpanding means anchor member mounted tooscillate about to actuate the latterin the direction of rotation ofsaid surfaces, vstops on said anchor member se# lectively anchoring theends of said segments,

cranks selectively engageable withthe ends of said segments and operableto expand the lat.- ter, a rin-g disposed within said surfaces andmountedfor angular movement about said axis, said ring being connectedto said cranks, and selectively controllablemeans for causing angularmotion of said ring with varying degrees of force.

3. A friction brake mechanism for use with a rotatable drum having'aninturned :flange at one end and two call surfaces, 'said'brake mechanismcomprising a non-rotatable anchor member, a friction element arranged toanchor on said member and adapted for radial vexpansion into grippingengagement with the internal surface nearest the open end of said drum,.an auxiliary anchor member mountedfor friction element,- expanding meansfor said element actuated by said auxiliary member,'an auxiliary`friction element arranged to anchor on said auxiliary member and adaptedfor expansion into gripping engagement with said other interl nalsurface, two axially engageable friction members drum with the drivingmember adapted for rotation with the -drum and the driven memberangularly movable and connected to said auxiliary element for'.expanding movement of the driven member in either directionlvfrofm anormal brake-released position, and means controlling the grippingengagement of said friction members.

4. A friction brake having, in combination, a

drum and two internal cylindrical surfaces rotatable about a commonaxis, aV

main friction eleaxially oiset internal cylindrioscillation `about'theaxis of said disposed adjacent the anged end ofsaid` the same uponangular ment expansi'ble into gripping engagement with one .of saidsurfaces, an auxiliary friction element expansible into grippingengagement with said other cylindrical surface, anchoring' means forsaid auxiliary element mounted to turn about said axis, means movablewith saidV anchoring means to expand said main element, expanding.energization of said operator, means for amplifying said actuating`force and applying the amplined force-to energize said brake including ameans for said auinliary element including a member mounted -within saiddrum for angular movement in the plane of drum rotation, power actuatedmeans self-contained within said drum to regulate the angulardisplacement of said member. and means variably controlling theenergize.- tion of said power means.

5. The combination of a main friction b'rake having a friction elementrotatable with a part whose motion is to be controlledand a secondelement'radially engageable with 'said first element and anchoredagainst rotation therewith,

a friction device comprising driving and driven friction elementsconcentric with the rotational axis of said part and adapted for `axialgripping engagement to Iderive an actuating force from the momentum ofsaid part, selectively operable means controlling the degree of suchengagement, and means for amplifying said actuating force and applyingthe amplified force to said brake to actuate the latter including a sec'ond friction device having a Vdriving member rotatable with said partand a' driven member radially engageable with the driving member byangular movement of `said driven element wherei byto derive an actuatingforce fromIthe momentum of said part, said driven member being'operatively connectedv to said anchored frictionele- I ment.

6. A friction brake for use with two internal cylindrical surfaces andan axially facing surface rotatable about a common axis in unison witlia part whose motion is to b'e controlled, said brake comprising a memberfrictionally engageable with said axially facing surface, an` auxiliaryfriction element adapted for gripping engagement with one of saidcylindrical surfaces and expansible by angular movementof said member,-anchoring means for said element movable about said axis and disposedwithin sai-dzcylindrical surfaces, a main friction'element adapted forgripping ensagement with said other cylindrical surface, stationaryanchoring means for said main element, and force amplifying meansmounted on said sta'- tionary anchoring Ameans for movement relativethereto and actuated bymovement of said movalble anchoring means,lsaidlast mentioned means being operable to expand said main lelement.

7. The combination of a main friction brake for applying a retardingeil'ect to a part whose motionvis to be controlled, a friction momentumoperator adapted when energized to derive an motionis to be controlled,a friction momensaid part, said second operator comprising an internalcylindrical friction surface rotatable with said part, a plurality offriction segments arranged in end to end relation within said 'surface,abutment anchors for said ends, and means actuated by said firstoperator to move one end orthe other 'of each segment away from itsanchor. Y

9. The combination of a main friction brake for applying a retardingeffect to a part whose motion is to be controlled, a friction momentumoperator adapted when energized to derive an actuating force from themomentum of said part, selectively operable means controlling'theenerglzation of said operator, and means for amplifying said actuatingforce and applying the amplified force to energize said brake including1ever mechanism and a second momentum operator energized by saidrstmentioned actuating force and deriving a secondary actuating forcefrom the momentum of said part, said brake and said second operatorhaving cylindrical friction surfaces'rotatable with Vsaid'pari'nand saidrst operator having axially engageable frictionA elements l onerotatable with said part.

said mechanism comprising a non-rotatable anchor member adapted to besupported Within said actuating force from the momentum of said part,

drum, almain friction element supported by said member and adapted forexpansion into engagement with said surface, Aa'second member rotatablysupported on saidV anchor member, a second l friction element anchoredon said second member and adapted for expansion. into engagement with asecond internal cylindrical surface rotat# able with said drum, andpower actuated means supported by said second member for movementtherewith and operablewhen energizedto moveV relative-to the secondmember and expand said second element. Y p

11. A friction brake having, in'combination,

an expanslble 4element having a non-rotatable anchor, a lining offriction material fastened to theouter periphery of said element, asecond expansible element having a circumferentially floating anchor, asecond substantially thinner lining fastened to the outer periphery ofsaid second element and correlated in width and thickness to said firstlining, selectively control- Vlable means for expanding said secondelement.

and expanding means for said firstV element actuated by circumferentialmovement of said floating anchor and operable to expand the elementunder a unit pressure substantially-greater than that applied to saidsecondelement.

12. A friction brake for use with a rotatable drum open at one end andtwointernal cylindrical sin'faces concentric with-the drum axis'and Yrotatable with the drum, said brake comprising an anchor member, a mainfriction element anchored on said member and vadapted for expansion, anauxiliary friction element adapted forV radial expansion and disposedadjacent but axially offset'relative to said main element, anchor# ingmeans for said auxiliary friction element .controlling the degree ofmounted on said member to turn about the axes of said elements,expanding means for said auxiliary element, actuating means for saidexpanding means including two friction rings mounted within saidauxiliary element substantially in the plane thereof, one of said ringsbeing mountable `for rotation with said drum and the other beingrotatable about said axes and connected to said expanding means, andselectively operable means controlling the degree ofv grippingengagement between said rings, said main and auxiliary friction elementsbeing engageableA respectively of said individual actuating meanstomovethe latter and cause expansion oi- 'said main braking member,separate means for moving the respective elements to expand the sameagainst their coacting rotatable surface, and selectively controllablemeans for actuating saidlast mentioned .means in unison.

16. A friction brake having, in combination, a main friction elementhaving a radially expansible outer peripheral surface, said elementhaving Y ends spaced apart on one side of the said surwith the surfacesof said drum which are respecf tively disposed adjacent and remote fromthe open end of the drum when said brake mechanism is mounted therein.

13. A friction brake having. in combination, a rotatable drum open atone end and closed at the other end and providing two internalcylindrical surfaces concentric with the drum axis with their centerlines axially spaced therealong, an anchor member disposed adjacent saidopen end and projecting into the drum, a main friction element anchoredon said member and expansible into gripping engagement with the one ofsaid surfaces nearer said anchor member and said open drum end, saidelement having circumferentially separable parts, an auxiliary frictionelement adapted for gripping engagement withzthe major circumferentiallength of the other cylindrical surface, anchoring means for saidauxiliary friction element mounted on said member to4 turn about saiddrum axis when the element is expanded against said drum. expandingmeans for said auxiliary element, selectively controllable actuatingmeans for saidexpanding means, and means actuated selectively accordingto the direction of movement of said anchoring means .fol-

lowing engagement of said auxiliary element with its rotatable surfaceto move one of said separable parts of said main element away from itsanchor on said member and in the direction of drum rotationV whileleaving the yother part iixed against its anchor.

14. A friction brake having, in combination, a non-rotatable anchormember, a mainV friction element anchored on said member and radiallyexpansible, an auxiliary'friction element adapted for radial expansion,anchoring means for said auxiliary friction'element mounted toturn-about the axisv of said main element, means connecting said movable.anchoring means and said main face, non-rotatable means anchoring saidvelement, an anchor member mounted to turn about the axis of saidelement, means connecting said anchor member and at least one of saidends to expand said element on movement of the anchor member, anauxiliary friction element having a radially expansible outer peripheryandv compris- Aing a plurality of annularly spaced separate partsproviding a. plurality of annular-1y spaced of ends angularly spacedfrom the ends of said main element, each of said parts being adapted toanchor on said member, and selectively control- -lable expanding -meansfor .said auxiliary element for applying individual actuating forcessimultaneously to ends of the different parts.

A17. A friction brake having. in combination.

two internal cylindrical surfaces axially offset and rotatable about a.common axis, a plurality of main friction segments arranged in end toend relation and expansible into gripping engagement with one of saidsurfaces, stationary stops associated with said adjacent ends foranchoring one or the other end, lever means operable selectively toengage one or the other of said segment ends and apply circumferentiallydirected actuating forces to the engaged ends, a second pair ofauxiliary segments arranged in end -to end relation and expansible intogripping. engagement with said other cylindrical surface, a membermounted to owillate about said axis and connected to said lever means toactuate the latter in the direction 'of roation of said surfaces, stopsonsaid member selectively anchoring the ends of said auxiliary sments,lever means operable selectively to engage the ends of said auxiliarysegments -and apply circumferentially directed forces to'the engagedends, and operating means operable selectively to actuate saidlastmentioned lever means in a direction determined by the rotation ofsaid surfaces.

friction element and operable to expand the latter upon movement awayfrom a normal brakereleased position, expanding means for said auxiiiaryelement, actuating means-for said expanding means including two axiallyly friction elements, one mounted on said movable anchoring means formovement relativrthereto about said axis,'and selectively operable:means t between said last mentioned friction elenents.

v 415. A friction brake bavlngdn comhimtion, a main friction braking'member cumferentially spaced parts adapted to anchor at one'of theirends and movable to 'expand and contractthe peripheryofthe individualmeans for actuating tbe rclllcetive parts toexpand said member,a'plurality'ot fricarrangedinendtoendrelatiiad- :lucent said member andadapted for radial exan anchor member mounted to oscillate about theaxis of said main friction member and providing anchors for eachA ofsaid elements,

18. A' friction brake for use with a drum and two internal cylindricalsurfaces axially offset relative to each other and rotatable in unisonabout the drum axis, said brake comprising a main friction elementadapted for. radial expan sion and contraction, non-rotatable meansanchoring said element, an anchor member mount-`edtotumabouttheaxiso'fsaidelement,xneans said anchor member and saidelement to expand the latter on movementof tle anchor' member in eitherdirection effects are built un in each of said parte and applied to'saidanchor member.

19. The combination of a rotatable part having adjacent frictionsurfaces concentric with acmnmon axis, a main non-rotatable frictionvelement radially movable into gripping engagement with one of saidsurfaces, a friction device comaxis of said part and providing an anchorfor said driven friction member, and means connecting said anchor memberto said main friction element to actuate the latter in response togripping engagement of said driving and driven members.

20. A friction brake for use with means providing two internalcylindrical surfaces concenhaving separable ends on one side thereof, amember for anchoring said ends mounted to turn about the drum axis, alever pivoted on said any for radial expansion of its peripheral surfacetrio with und rotatable in unison about s common axis, said brakecomprising a main friction element adapted for engagement with one ofsaid surfaces and having circumferentially separable ends, an anchor forsaid ends, lever mechanism projecting inwardly from and fulcrumed adja-1 cent the friction surface of said element to 'swing' Y in eitherdirection away from a normal-'brakereleased position and move one end orthe other of said element circumferentially away lfrom said anchor, amember mounted to turn about the drum axis and connected to said levermechanism to actuate the latter and expand said element, an auxiliaryfrictionelement being adapted for engagement with said other drumsurface and having separable ends adapted to anchor on said member, andcontrol means operable selectively to move one or the other ends of saidauxiliary element circumferentially away from` its anchor in thedirection of rotation of the drum surfacef o with which the auxiliaryelement is associated.

21. A friction brake for use with a rotatable' drum andA two internalcylindrical surfaces ro' tatable therewith, said brake comprising a mainfriction element expansible into gripping engagement with one of said,surfaces when the brake is mounted within said drum, an auxiliaryfriction element extending around i the other surfaceand havingseparable ends on one side thereof, a member anchoring said ends andmountedv of said ends in the direction of drum rotation toward the otherend, whereby to expand said auxiliary element against its coactingsurface and cause said anchor member to shift angularly, x and expandingmeans for said main friction ele# ment actuated bymovement of saidmember in either direction away from normal brakereleased positionfollowing expansion ofsaid auxiliary eiement. Y

22.,A friction-broke adapted to be mou'tod withinl a rotatable drumhaving two axially spaced internal cylindrical slu'faces said'brake:when so mounted comprising a'main friction element expansible intogripping, engagement with one of said surfaces, an auxiliary lfrictionelement expanding around the other surface and4 chor member andswingable in opposite directions from a normally brakereleased positionto separate said ends -circumferentially, means 'for swinging said leverin a direction determined. by the direction of drum rotation to causeone of said ends to be moved circumferentially away from'its anchonandmeans connecting said mem- A b er and said main friction element toexpand the' latter in response to movement of the member in eitherdirection away from normal brakereleased position following expansion ofsaid auxiliary element.

23.' 'A friction brake having, in combination, a main friction elementadapted for radial expansion of its peripheral surface, an auxiliaryfriction element adjacent said main element having separable ends on oneside thereof and adapted upon separation of said ends, a member4anchoring said ends and mounted to turn about the axis of saidsurfaces, an expanding device mounted on said anchor member for movementrelative thereto in either direction away from a normal brake-releasedposition and operable in such movement to shift one or the other of saidends away from its anchor according to the direction of rotation ofthedrum surface with which said element surfaces engage, actuating meansfor said expanding device carriedby said'anchor member and adapted formovement relative thereto, and means connecting said member and saidmain friction element and operable to expand the latter in response tomovement of said member in either direction away from a normalbrakereleased position.4

24. A frictionbralse having, in combination, a main friction elementadapted for expansion of its peripheralsurface byseparation of its endscircumferentially, a non-rotatable'bwcking plate providing an anchor forsaid e1ement,' aring journaled o n said backing plate on the inner sidethereof and within said friction element to turn about the axis of saidelement, an auxiliary f radially Vexpansible friction element havingseparable ends'on one side thereof adapted to anchor on said ring at apoint angularly spaced loA from the ends of said mam motion element, ex-

.to turn about the drum axis, means-carried by l Asaid member andmovable relative thereto Vto cause selective circumferential movement ofone Y -lectively in accordance with the direction of lrogagement Withsuch panding means for said auxiliary element mounted on said ring formovement relative thereto. and means connecting said member and said`main friction element and operable to separate the ends thereof andexpand the element in response to movement of said member in eitherdirecton away from a normal brakereleased position following grippingengagement between the auxiliary element and its coacting rotatablesurface. v

25. A friction ,brake having, in combination,

main and auxiliary frictionelements having substantlally completeannular external friction sur` facesand each having circumferentiallyseparable ends, a member mounted .to turn about the axis of saidsurfaces and providing anchorage for said auxiliary element, meansoperable setation ofthe friction surface with whichsaid element surfacescoact to actuate one or the other end'of said auxiliary element toexpand the full length -of the latter 'into effective grippingencoacting surfaces, and means operable selectively by movement of saidmember lin either direction following c!!` of said auxiliaryl element toexpand the full length of said main friction element, one of saidelements being divided into a plurality of angularly spaced' partsindividually anchored and actuated ,so/ as to constitute the seats ofseparate self-energizing eiects.

26. A friction brake having, in combination, a

main friction element having a radially expandible outer peripheralsurface, a member movable in opposite directions about the axis of saidsur face, means actuatedselectively by movement of said member in eitherdirection away from a normal braise-released position to expand saidelement, a plurality of auxiliary friction elements angularly spacedaround said axis for expansion into gripping engagement withsubstantially the entire circumference of a rotatable drum surface,means on said member providing anchors for opposite ends of each of saidauxiliary elements,

a plurality of actuating devices for each of said auxiliary elementsrespectively associated with the opposite .ends thereof and movableselectively, in either direction to move one end of the associatedelement circumferentially away from its anchor and expand the elementagainst its Vrotating surface, and, means for operating one expandingdevice .of each of said auxiliary elements in unison and incorresponding directions, whereby to cause separate self-energizingforces to build up in the respective auxiliary elements Y substantiallythroughout the lengths of the lat- 27. A friction brake having, incombination, a. mainfriction 'element having a. radially expandiblekperipheral surface, a nonfrotatable anchor therefor, a member mounted onsaid non-rotatl able anchorto turn about the axis of said sur' face,means actuated selectively by movement of said member in eitherdirection away from'a normal brake-released position to expand saidelement, an auxiliary Vfriction element adjacent to and coaxial withsaid main element and having a Vradially expandible peripheral surface.said auxiliaryv element being anchored on said memfb'er, an actuatingmember -carried by and journaled on'said-member to turn relative theretoabout said axis, and expanding means for said auxiliary element actuatedselectively in response s to turning of said actuating memberV relativeto saidanchor member;` f f 1,28. A friction brake adaptedto be mountedwithin`a rotatable' closed at one end and open at the other' androtatable with two internal cylindrical surfaces' disposedv with theircene ter lines voiiset relative to each other along said axis, vsaidbrake lwhen mounted within said drum A'comprising a main frictionelement having sepf .arable ends and expandible into gripping engagementwiththe one of said surfaces nearer the open end of the drum,` anon-rotatable anchor;

- ing means for saidends, a member .iournaledmr said anchoring means toturn about -the Vdrum axis, means actimted selectively by movement of,said member inopposit'e directions away from mem ber in either ondelement moves angularly with of, a member anchoring said ends ment ofone of said'ends in the direction a normal brake-released position tomove the respective ends circumferentially away from` their anchors andexpand said element, an auxiliary friction element having separable endsadapted to anchor on said member, a friction element disposed within thedrum and adjacent the closed end thereof and having a frictionl surfacerotatable with the drum and facing axially toward the open end thereof,a driven friction element adapted for gripping engagement with saidaxially facing surface to move therewith in the direction of drumrotation, means actuated by said driven friction element and operableselectively tomove one end or the other of said auxiliary elementcircumferentially to expand the element against its rotating surface andthereby cause angular motion of said member, and means selectivelycontrolling the gripping engagement between said driven element and saidaxially facing surface.

29. A friction brake mechanism having, in combination, an'expansiblefriction element having a non-rotatable anchor, a lining of frictionmaterial carried on the external surface of said element, a. secondexpansible friction 4element coaxial with respect to said first elementand .having a circumferentially floating anchor, a second substantiallythinner lining carried on A second element.A

the external surface of said means connecting said floating anchor tosaid first element to expand the element as saidsecselectivelycontrollable means for expanding 'said second element, said elements andthe expanding means being constructed toproduce greater unit pressureson said iirst lining than on the second and wearing out of the two afterapproximately the same length of service use;

30. A friction brake for use with` a rotatable drum and two separateinternal cylindrical surfaces rotatable therewith, said brake comprisinga main friction element having an external periphery expansible int`ogripping engagement Awith one of said vsurfaces when the brake isAmounted within said drum, a non-rotatable anchor for said main frictionelement having an axially projecting hub concentric with and disposedWithin said-` friction element,' an auxiliary friction element extendingaround face and having separable ends on the other,l surone sidethereand journaled on said hub to turn about the drum axis, meanscarried by said member and movable relave thereto 'to causeselectivecircumferential moveof drum rotation toward the other end,whereby to expandsaid auxiliary element against its enacting surfacesaid anchor member to shift angular-lv. and friction element actuated bymovement of said brake-reelased position following expansion of saidauxiliary-element.

' Jonn anonce om.

the drum, and

expanding means for said main direction away from normal,

